Started essentially as a gas station, it now generates annual sales of $40 million and claims the state's largest distribution of propane and propane-fueled products. It also makes dry ice, hydrogen and other gases for the home health care, industrial and leisure markets.

Despite ownership changes and rebranding, the company is still known to local folks simply as Gaspro.

It has more employees with more than 20 years' tenure than employees who have worked for the company five years or fewer.

Among the nearly 120 employees are multiple generations of about half-a-dozen families.

It kind of goes back to the "plantation mentality," said Diane Brittain, Maui branch manager, who will start her 45th year with the company next month.

"That's how we feel ... you work for a company, the company's good to you, you just commit. You're like a family ... and you stick with them."

She was placed in a secretarial job at age 20 and in a male-dominated industry. Brittain was promoted to management in the mid-1970s.

The company's specialized nature is only a small part of employees' longevity, said Mark Mahler, area vice president.

"They have always found a way to enhance the customer's experience to make them want to come back," he said.

"Coming in from the mainland, when I found the culture in this organization was committed to taking care of the customer, and I wasn't just walking in on a bunch of paycheck-collectors, it was really refreshing."

"Customer-facing or not, whether it's guys in the plant, or in distribution or in customer service ... they all understand that they have a very important role in the ultimate experience the customer has with us and they take it very, very seriously. I think that ... has kept us here for 100 years and will keep us here for another 100," said Mahler.

The company was established in 1909 as Acetylene Light and Agency Co. Ltd. at South and Kawaiahao streets. It supplied acetylene gas and components for automobile headlamps — before electric headlights — as well as gasoline and other products.

Allan Renton and a partner bought into the business in 1919 and renamed it Hawaiian Gas Products the following year.

That's Renton, as in the Ewa road named for another family member who was an Ewa Plantation manager. The family's sugar-business roots took hold in Kohala on the Big Island, before relocating to Oahu, said Allan D. Renton, grandson of the late founder.

His grandfather "knew every employee in the company by their first name and it was quite a family kind of organization. There are still long-standing families that we are still in contact with," he said.

His father, Allan H. Renton, started with the company around 1950 and took the helm in the mid-1970s.

Along the way it became a manufacturer for niche markets. Its acetylene and oxygen was used by the sugar industry for metal braising for its machinery. Also for the sugar industry, it made lime, an outgrowth of CO2 production for beverage-bottling; it also made bottles and pipes.

"I think we were the next to the last independent oxygen manufacturer that was swallowed up by the big industrial giants," in 1980, said the older Renton.

The family retained the acreage under the Kamehameha Highway facilities until land sales to First Hawaiian Bank in 1991 and last year dissolved its ties.

Banners will proclaim the centennial at Gaspro branches that will serve cake and juice and offer customer discounts.

A "grandiose" celebration was planned, but given the economy, the decision was made to save money and keep people employed, Mahler said.

"That's what I would do if I were in their shoes," the older Renton said. "They all have families."